Magnetoresistive devices such as magnetic sensors and magnetic memory cells include magnetic materials where the magnetic moments of those materials can be varied to provide sensing information or store data. For example, in certain magnetic memory devices, the voltage drop across a magnetic tunnel junction (MTJ) can be varied based on the relative magnetic states of the magnetoresistive layers within the memory cell. In such memory devices, there is typically a portion of the memory cell that has a fixed magnetic state and another portion that has a free magnetic state that is controlled to be either parallel or antiparallel to the fixed magnetic state. Because the resistance through the memory cell changes based on whether the free portion is parallel or antiparallel to the fixed portion, information can be stored by setting the orientation of the free portion. The information is later retrieved by sensing the orientation of the free portion. Such magnetic memory devices are well known in the art.
Manufacturing magnetoresistive devices, including MTJ devices, includes a sequence of processing steps during which many layers of materials are deposited and then patterned to form a magnetoresistive stack and the electrodes used to provide electrical connections to the magnetoresistive stack. The magnetoresistive stack includes the various layers that make up the free and fixed portions of the device as well as one or more dielectric layers that provide at least one the tunnel junction for the device. In many instances, the layers of material are very thin, on the order of a few or tens of angstroms.
In some applications, magnetoresistive devices are included on the same integrated circuit with additional surrounding circuitry. For example, magnetoresistive sensors may be included on an integrated circuit with a microcontroller or other processing circuitry that utilizes the information collected by the sensors. In another example, magnetic random access memory (MRAM) is included on an integrated circuit with a processor or some other logic circuitry. The process flows associated with forming magnetoresistive devices are typically unique with respect to those process steps used to form the surrounding circuitry on such integrated circuits. Therefore, it is desirable to provide magnetoresistive devices and techniques for manufacturing integrated circuits that include magnetoresistive devices that allow for efficient integration with respect to established integrated circuit manufacturing process flows.